Lawn mower sharpener



May 13, 1952 H. c. BURNHAM 2,596,098

LAWN MOWER SHARPENER Filed April lO 1951 Patented May 13, 1952 UNITED STATES PATENT OFFICE LAWN MOWER SHARPENER Harry C. Burnham, Portland, Oreg.

Application April 10, 1951, Serial No. 220,179

(ci. 'zc-san 3 Claims. l

This invention relates to a method and apparatus for sharpening lawn mower blades and to an improved lawn mower blade produced thereby.

It is among the objects of the invention to provide a new method for sharpening lawn mower blades whereby the blades are quickly and easily sharpened and each bladeis provided with a longitudinally-extending, concave surface in its forward face adjacent and substantially parallel to its cutting edge to provide a more durable cutting edge on such a blade and to provide an improved sharpening tool for carrying out the above process and producing a lawn mower blade of the character indicated, which tool is of small size and simplified construction and can be easily applied to and reciprocably moved along a lawn mower blade to reduce a rounded edge on such a blade and restore the sharp cutting edge necessary to satisfactory operation, which Will produce a shallow, rounded groove or depression in the forward face of the blade at the cutting edge thereof to give to the cutting edge portion of the blade a hollow ground formation, which includes a replaceable or interchangeable le or abrader and means for locking such iile or abrader in position with any predetermined portion of its abrading surface presented for use, and which is strong and durable in construction, economical to manufacture, and easy to use.

Y Other objects and advantages will become apparent from a consideration of the following description and the appended claims in conjunction with the accompanying drawing, wherein:

Figure 1 is a front elevation of a lawn mower Sharpener, illustrative of the invention;

Figure 2 is a cross-section on the line 2 2 of Figure 1 with the parts in a somewhat different operative position from that illustrated in Figure l; and

Figure 3 is a cross-section on the line 3-3 of Figure 1.

With continued reference to the drawing, the improved lawn mower Sharpener comprises, in general, a frame I0, an abrader I I, a clamp block I2 for the abrader, and a set screw I3 threaded through a portion of the frame and carrying the clamp block I2.

The frame I comprises a at back portion I4 shaped to provide a generally triangular portion imposed at its base on one edge of a generally rectangular portion. A lug I projects perpendicularly from the back portion i4 at the apex of the triangular formation, and is provided with an internally Screw-threaded hole or aperture I5 extending therethrough. A rib ll projects substantially perpendicularly from the back portion along said one edge of the-rectangular formation of the back portion and is provided with a notch I 8 of rectangular shape substantially symmetrical with the mid-length location of the rib, and a guide tongue I9 projects from the back portion at the opposite or outer edge of the rectangular formation and has a length substantially equal to the length of the notch I8 in the rib., This guide tongue is shaped to provide a substantially sharp bearing edge 2D directed toward the outer edge of the rib II, and between the tongue I9 and the rib I'I, the back portion is provided with a convex formation or bead 2| which also serves as a guide surface in cooperation with the bearing edge 20 of the guide tongue.

The abrader II, as illustrated, ls a file of generally cylindrical shape, but slightly tapered toward its opposite ends, and provided with a concentric, longitudinally-extending bore. Thisfle II has a length slightly less than the length of the notch I8, and a shaft 22 extends through `the bore of the lile and is received at one end in a recess provided in the rib II at the corresponding end of the notch I8. As its opposite end, the shaft 20 is received in a socket 23 provided in the rib at the opposite side of the notch I8, the socket 23 being open at the side of the rib opposite the guide tongue I9, so that the file or abrader II can easily be removed from and assembled with the frame I0.

While the abrader has been illustrated as a le of generally cylindrical shape, it is to be understood that this abrader may lbe provided as a stone of abrasive material, as a core having a coating of abrasive material thereon, or as a smooth body of' hard material for lapping an abrasive compound against a mower blade, and may be of rectangular or polygonal, as well as circular cross-sectional shape, without in any way exceeding the scope of the invention.

The clamp block I 2 is of rectangular shape and has therein a T-shaped recess 24 opening to the top surface and one end surface of the block. The screw I3 has an externally screw-threaded portion 25 threaded through the lug I5 and has, on one end, a cylindrical head 26 received in the larger part of the T-shaped recess 24. Between the head 26 and the screw-threaded portion 25 the screw has a smooth, reduced shank 2'I recelved in the smaller or narrower portion of the recess 24, so that the block I2 is iirmly attached to the screw I3 by the cylindrical head 261. The block is held against separation from the screw by a locking pin 28 which extends transversely 3 f through the block near the end of the block to which the recess 2d opens. On its end opposite the head 26, the screw may be provided with any conventional form of screw head 29 to facilitate threading the screw through the lug I5.

In its lower side, the block I2 is provided with a V-shaped groove 36 of a size to firmly engage the upper portion of the abrader I I, and is provided withbevelled edges 3| and 32 at respectively-opposite sides of the groove 30.

It will be noted that the rib I'I is slightly curved longitudinally, this curvature being substantially the same as the curvature of the reel blades of a lawn mower.

In using the sharpener, the reel .,structureof a lawn mower may be removed from the mower and clamped in a suitable vise.. The Sharpener is then operatively engaged with one of the reel blades by inserting the cutting edge of the reel blade between the abrader I I tongue- I9.; assuming'that'the clamp block I2 is in rm engagement with the abrader. The blade is anelongated'member of elongated, rectangular, cross-sectional shape havingone edge beveled to provide a cutting edge, and the Sharpener is tilted' until the abrader bears rmly on the forwardsideof itheblade at the cutting edge or the latter and is then manually moved back-'andforth longitudinally of the blade substantially parallel to the cutting edge until the rounded edge' portion of theblade has been removed and the,` cutting; edge restored, as particularly illus-- trated inFigure 2. By' using an abrader of substantially `vcircular cross-sectional shapev the tool will'producel a shallow, rounded groove or recess in the blade at the cuttingedge of the'latter, thus giving" the blade. a hollow-ground formation Whichgreatlyincreases the useful life of the cutting edgesotheblades and alsok facilitates resharpening thereof.

.Ifone portion of theabraderl I becomes'worn, so'that'the abrader does not/operate efficiently, theescrew- I3 is loosened and the Vabra-der turned to'bring a-'new portion ofY itsfsu'rface to abrading position,` after which the serew- I3 `is tightened tofforce the' clamp blockr I2 yagainst the abra-der and-firmly-` hold theA abrader-in its new position. Thisfmaybe continued until an abrader is cornpletely expended, whereupon the one abrader/ may befremoved byy loosening the screw I3 and a new abrader placed on the shaft 2QA and the shaft receded inthe-rib I'I. It'is also possible-*to use abraders of different coarseness -to provide rapid cuttingl` at the beginning` of the sharpening operation, and finer cuttingV near the end ci such operation to provideia cutting edge of maximum sharpness.

The abrader may be also used in the same general manner to sharpen 'the straightlor bottoni blade of' the mower.

The frame I0 and the clamp block I2 may be formed of any suitablematerial, such as steel, aluminum orfbrass, the screw I3 and shaft 22 are preferably formed of suitable steel, while the abr-ader II may be formed of specially hardenedsteel or of va suitable abrasive compound.

The invention may be embodied in other specific formswithout departing from the spirit or essential 1 characteristics thereof. The present embodment'is,therefore, to be considered in all respects asillustrative and not restrictive, the scopeiof theinvention being-indicated by the appended' claims rather than by the foregoing dcscription, and all changes which come within the.' meaning and range of equivalency of the and Y the guide 4 claims are, therefore, intended to be embraced therein.

What is claimed is:

l. A hand to'ol for sharpening a lawn mower blade having parallel faces and a beveled edge comprising a frame including a rst portion of substantially triangular shape and a second'portion of substantially rectangular shape extending along the base edge of said. portion oftriangular shape, a rib projecting from Y one side of said frame along the base edge of said rst portion and having an elongated notch intermediate its length, an elongated abrader of substantially circular cross-sectional shape disposed in said notch andsupported at its ends on said rib at the ends of said notch, said abrader being adapted to engage'onefaceiofi anassociated blade adjacent the bevelededge of the latter and provide in the face ofthe blade engaged thereby a shallow groove or" rounded cross-sectional shape terminating laterally at thebeveled edge-of the blade; a tongue extending fromsaid one sideof the framev along the edge `of said second portion remote from `said rst portion and terminating outwardly` in a bearing edgefadapted to engagethe face-off an associated blade opposite the 'blade face engaged by said abrader inI opposition to the latter', a-fl'at bead on said one side of Asaidv frame-between said abrader and said tongue-adaptedto engage-the beveled edge of an associated bladefand guide the tool along the; edge ofabla'de, alclarnpv block disposed againstsaid one` side' ofitile-framel and engagingsaid abrader atthe side Aroithe latter remote from said tongue, and means-connected 1 between said frame'andsaidclampblock'releasably holding said clampblock in engagement Vwith said abrader; Y

2. A hand toolV for sharpeninga lawn-mower blade having 'parallel faces-"and a? beveled edge comprising a frame including af first portion of substantially triangular shapeand a second portionzof substantially-rectangularjshape 'extending along the'base edge'of` said 4portieri of triangular shape,ga rib projecting from one sidei of'sai'd frame along the .base edgeofsaidirst portion and havingian' elongated' notchiintermediate' its-length, an elongated` abradenof`v substantiallyV circular cross-sectional'shapedisposed'in said notch and supported atits endsionsaid rib atlthe ends of said notch, said. abrader being adaptedto engage one face of, 'an associatedbladeadjacent the beveled edge. of thelatterand" provide inthe face of the blade, engaged. thereby a shallow groove of rounded cross-sectional' shape terminating laterally at theV beveled` edgeV4 of the blade, a tongue extending from said one side of .the frame along the edge of said second portion remote. from said rst portion and terminating outwardly in a bearing edge adapted to engagetheface ofv an associated blade opposite the blade face engaged byV said abrader 4in opposition to the latten-anat bead on, said one side ofY said frameebetween .said abrader and sai-dtongue adapted` to engage the beveled edge-of an associated blade and guide the tool along the edgeof the latter, a clamp block disposed against said one side of the frameand engaging said abrader at the side of the latter remote from said tongue, a .lug' projecting: from said one side of said framefv at theV side ofV said clamp block remote from saidabrader'and having a tapped hole extending `therethrough and directed toward; the adjacent sideLofysaid clamp block, and a set' screw threaded'through th'e tappedhole in said lug and'bearing .at one end against said clamp block to force the latter against the adjacent side of said abrader.

3. A hand tool for sharpening a blade having substantially parallel faces and a beveled edge providing a cutting edge along the adjacent edge of one of said faces comprising a flat frame adapted to be moved back and forth along the beveled edge of an associated blade, an abrader of rounded cross-sectional shape carried by said frame in position to engage one face of an associated blade adjacent the cutting edge of the blade, a tongue projecting outwardly from said one side yof said frame in a location spaced from said abrader and terminating outwardly o1 said frame in a bearing edge adapted to engage the face of an associated blade remote from said abrader in opposition to the latter, a guide bead on said one side of said frame between said abrader and said tongue adapted to engage the beveled edge of an associated blade and guide HARRY C. BURNHAM.

REFERECES CITED The following references are of record in the of this patent:

'UNITED STATES PATENTS Number Name Date 555,974 Roberts et a1 Mar. 10, 1896 584,457 Brown June 15, 1897 765,492 Knowlton July 19, 1904 927,131 Dow July 6, 1909 1,263,666 Hastings Apr. 23, 1918 1,386,341 Kansen Aug. 2, 1921 

